"A Clear Future for our River"

Harriet Alvis

River Marden 2018 fisheries improvements

Project background

In 2017, Bristol Avon Rivers Trust (BART) applied to the Environment Agency’s ‘Fisheries Improvement Fund’ following a walkover survey of the entire length of the river and several small improvement projects over recent years.

The River Marden rises in Calstone Wellington, Wiltshire and runs through the town of Calne, then
through pasture and villages before joining the Bristol Avon to the north east of Chippenham. Water
Framework Directive (WFD) status along the river varies between Good and Moderate (in the lower
catchment). The river has a number of issues along its length that are resulting in the degradation of
both water quality and fisheries habitat. These include river impoundment and fish passage
restrictions by weirs, as well as the historic straightening of large sections of river.

The objective of this project was to contribute to addressing some the main issues affecting the river.

 

2017-2018 Improvement works

Weir fish passage feasibility studies

The River Marden is predominantly a coarse fishery (notably roach, dace, chub, perch, pike, bream,
barbel, bleak and gudgeon) though wild brown trout are found in large numbers throughout the
river. There are a number of obstructions along the river which impact on the movement of fish and
also the quality of habitat upstream of the obstruction i.e. the creation of a silted bed substrate and
impounded flow conditions.

BART identified three weirs; Moses Weir, Stanley Weir and an unnamed bedrock weir where fish passage and, if feasible, upstream riverine habitat improvements following the weir removals, would gain significant benefits for the river. Hydro-Morph Ltd was commissioned by BART to undertake an initial site visit and pre-feasibility investigation of possible options for improving fish passage and upstream habitat at each structure. These reports have been completed and provided to the Environment Agency Fisheries and Biodiversity team.

 

In-stream habitat improvement works

This element of the project worked on an overshaded and straightened section of the river
downstream of Chilvester Hill, Calne. Low cost improvements were delivered here including coppicing to re-instate a 60:40 ratio of shade to light. In-stream wooden flow deflectors were
constructed from bankside materials to help re-meander the river within it’s straightened banks.

In total BART constructed 11 structures, which will have a variety of benefits including increased
flow diversity, cleaner spawning gravels and providing enhanced fish cover for fry and adult fish. We
are looking forward to seeing how these structures develop as similar structures we have built on
the river in Calne have been very well received and had an almost immediate impact on the river
and the sport provided. The Marden is a relatively spatey river so we anticipate that the structures
will be well hidden by silt accumulation in a year and will form part of a newly meandering bankside
within 2-3 years. We will continue to monitor the progress of these structures as this occurs.

 

Figure 1. A ‘pinch point’ created with a wooden berm which will encourage flows to scour the gravels, flushing out silt and improving fish spawning potential.

 

Figure 2. Alternate berms constructed to re-form a meander within the banks of this straightened section.

 

Boulder weir removal

BART’s survey work on the Marden identified two boulder weirs immediately above the confluence
of the river with the Bristol Avon at Chippenham. The weirs presented a barrier for smaller, weak
swimming species as they were only passable in high flow conditions. The lower sections of the
Marden have important spawning gravels and increasing access to these will help gravel spawning
species increase recruitment. The lower Marden also acts as an important refuge when the main
river is in spate. The weirs were also contributing to silt build up in the stretch of river above them
which was having an adverse effect on fish spawning as the riverbed gravels had become smothered
in sediment.

The two boulder weirs were removed as part of this project and the once uniform deeper section of
river with slow flows, is now shallower with riffles, exposed gravel bars and less silt deposition
creating new potential spawning grounds. BART will now leave the stretch to adjust to the new
conditions for a year before reassessing whether there is a need for any follow up habitat work.

 

Figure 3. Before and after – removal of one of the boulder weirs.

Thanks to all of our fantastic volunteers for their help with this project, to the landowner, land agent and tenant farmer for their help and enthusiasm and of course to the Environment Agency for funding these works. A huge thank you also to Wroughton Angling Club and Calne Angling Club, without whom this project would not be possible. We are looking forward to continuing to improve the Marden!

New BART/University research students

BART are pleased to welcome our newest University research students this month from the University of Bristol who will be continuing our water quality monitoring along tributaries of the Bristol Frome, this time looking at potential urban sources!:

“We are from the University of Bristol, School of Geographical Sciences currently studying towards our BSc in Geography. We are working in partnership with Bristol Avon Rivers Trust to assess for pollution levels from the two brooks running from separate neighbouring housing estates. During this research we will be implementing various different techniques and procedures in order to collect the data required to research this aim and test it effectively.”

Thank you and we are looking forward to seeing your results!

Can you help us to improve the River Marden in Calne, Wiltshire?

We are looking for volunteers to take part in a river restoration project which is taking place from 26th February – 2nd March and on the 5th and 7th March 2018. Work days will be from 10am – 3.30pm but you are welcome to come for as many days and for as long as you like.

The work will involve working on the bank and in the river helping to install woody habitat to improve flow, depth and habitat diversity for wildlife. Activities will include hand sawing, post banging and dragging branches. All equipment, including waders, tools and gloves, will be provided but you will need warm and waterproof clothing, food and drink and will need to make your own way to the site.

Volunteering with us is a great way to get outside, meet other like-minded people and do something positive for our local rivers!

For further information and to sign up, please email Harriet on harriet@bristolavonriverstrust.org

Rod licence funds – Environment Agency reports

The Environment Agency has today released the annual fisheries report detailing how rod licence income was distributed by the agency and its partners to protect and enhance angling and fisheries. The report details aspects of fisheries including money used to restock England’s rivers, enforcement and participation.

The Wessex report, featuring our weir removals on the Wellow Brook near Bath, can be found here.

Other reports can be viewed here.

 

The Bristol Avon – our Blue Planet

From where we are sat in the centre of Bristol or the more rural areas of the Bristol Avon Catchment, we rarely consider how our livelihoods and environments are linked to the sea. But in reality, our everyday actions have a direct impact on the health of our oceans, and a key part of this link is our rivers.

Rivers are a major pathway for plastic waste, washed into rivers from land during heavy rainfall events before flowing into the sea. In fact, it was reported that ‘just 10 rivers carry 90% of the plastic polluting our oceans’. This problem is not limited to developing countries and is ongoing in British waterways. Rivers are also suffering the same issues with plastic waste as we see on ocean awareness programmes such as the fantastic Blue Planet.

Plastic waste in the River Thames (Credit: Steve Taylor ARPS/Alamy Stock Photo)

Not only this, but toxins that run off from land, from urban and agricultural sources, bind to plastics in the ocean.  It is now well known that these various sized plastics are ingested by a range of organisms from plankton, to fish and birds and cetaceans. These toxins prefer to bind to fatty layers than plastics so enter the bodies of those that ingest them. In this way, these toxins enter the food chain and accumulate in larger animals such as the fish that we eat, posing a real threat to human health.

So how can you help?

Well, we have the potential to stop ocean waste at its source – by preventing waste from getting into our rivers and therefore into our oceans. BART run a number of riverbank litter picks throughout the year, so keep an eye on our volunteering page to get involved with these. We have also produced a guidance pack to help community groups to run their own litter picks, including risk assessments, blank posters and how to dispose of waste collected that we are happy to share (contact harriet@bristolavonriverstrust.org). There are some other really great organisations out there that are running litter picks in your area, such as local ‘Friends of’ groups and organisations such as Surfers Against Sewage. We are happy to help you find local groups you can get involved with, just get in touch! Or how about starting your own?

However, the best approach is to reduce the amount of single use plastics that we are using, for example using reusable cups, bags and other containers and buying from local shops such as greengrocers where you can purchase loose vegetables that are not in plastic packaging. We love the great Refill Bristol scheme started by City to Sea that is now going national and encourages business owners to put up stickers promoting that they are happy to fill up refillable bottles!

So, in summary, looking after our rivers is a fundamental step in protecting our oceans!